• Component Description
• Eligible Sample
• Description of Laboratory Methodology
• Data Processing and Editing
• Laboratory Quality Assurance and Monitoring
• Analytic Notes
• Codebook
  • SEQN - Respondent sequence number
  • LBXBPB - Blood lead (ug/dL)
  • LBDBPBSI - Blood lead (umol/L)
  • LBDBPBLC - Blood lead comment code
  • LBXBCD - Blood cadmium (ug/L)
  • LBDBCDSI - Blood cadmium (nmol/L)
  • LBDBCDLC - Blood cadmium comment code
  • LBXTHG - Blood mercury, total (ug/L)
  • LBDTHGSI - Blood mercury, total (umol/L)
  • LBDTHGLC - Blood mercury, total comment code
  • LBXBSE - Blood selenium (ug/L)
  • LBDBSESI - Blood selenium (umol/L)
  • LBDBSELC - Blood selenium comment code
  • LBXBMN - Blood manganese (ug/L)
  • LBDBMNSI - Blood manganese (umol/L)
  • LBDBMNLC - Blood manganese comment code

National Health and Nutrition Examination Survey

2011-2012 Data Documentation, Codebook, and Frequencies

Cadmium, Lead, Total Mercury, Selenium, & Manganese - Blood (PbCd_G)

Data File: PbCd_G.xpt

First Published: September 2013

Last Revised: NA

Component Description

Lead

Lead is a known environmental toxin that has been shown to deleteriously affect the nervous, hematopoietic, endocrine, renal, and reproductive systems. In young children, lead exposure is a particular hazard because children more readily absorb lead than do adults, and children’s developing nervous systems also make them more susceptible to the effects of lead. The primary sources of exposure for children are lead-laden paint chips and dust as a result of deteriorating lead-based paint. The risk for lead exposure is disproportionately higher for children who are poor, non-Hispanic black, living in large metropolitan areas, or living in older housing. Among adults, the most common high exposure sources are occupational. Blood lead levels measured in previous NHANES programs have been the cornerstone of lead exposure surveillance in the U.S. The data have been used to document the burden and dramatic decline of elevated blood lead levels, to promote the reduction of lead use, and to help to redefine national lead poisoning prevention guidelines, standards, and abatement activities.

Cadmium

A cadmium assay is performed to identify cases of cadmium toxicity. Occupational exposure is the most common cause of elevated cadmium levels.

Manganese

The greatest demand for manganese is for the production of iron and steel. In addition, it is a key component of low-cost stainless steel and certain aluminum alloys. At low concentrations, it is used to decolorize glass, while at higher concentrations, it is used to make violet-colored glass. Manganese dioxide, besides being a useful pigment, is a catalyst and a component of certain dry cell batteries. Potassium permanganate is a potent oxidizer and disinfectant. Manganese (in the form of manganese ions) is an essential trace nutrient in all known forms of life. On the other hand, excess manganese is toxic.

Total Mercury

Uncertainties exist regarding levels of exposure to methyl mercury from fish consumption and potential health effects resulting from this exposure. Past estimates of exposure to methyl mercury have been obtained from results of food consumption surveys and measures of methyl mercury in fish. Measures of a biomarker of exposure are needed for improved exposure assessments. Blood mercury levels will be assessed in two subpopulations particularly vulnerable to the health effects from mercury exposure: children 1–5 years old and women of childbearing age.

Blood measures of total and inorganic mercury will be important for evaluation of exposure from exposure to mercury in interior latex paints

Selenium

Selenium salts are toxic in large amounts, but trace amounts are necessary for cellular function in many organisms, including all animals. Selenium is a component of the antioxidant enzymes glutathione peroxidase and thioredoxin reductase (which indirectly reduce certain oxidized molecules in animals and some plants). It is also found in three deiodinase enzymes, which convert one thyroid hormone to another. Selenium requirements in plants differ by species, with some plants requiring relatively large amounts, and others apparently requiring none.

Eligible Sample

Participants aged 1 year and older who do not meet any of the exclusion criteria are eligible.

Description of Laboratory Methodology

Whole blood specimens are processed, stored, and shipped to the Division of Laboratory Sciences, National Center for Environmental Health, and Centers for Disease Control and Prevention for analysis.

Detailed instructions on specimen collection and processing can be found in the NHANES Laboratory/Medical Technologists Procedures Manual (LPM). Vials are stored under appropriate frozen (–30°C) conditions until they are shipped to National Center for Environmental Health for testing.

Whole blood lead (Pb), cadmium (Cd) , total mercury (THg) manganese (Mn), and selenium (Se) concentrations are determined using inductively coupled plasma mass spectrometry. This multi-element analytical technique is based on quadrupole ICP-MS technology. Coupling radio frequency power into a flowing argon stream seeded with electrons creates the plasma. Predominate species in the plasma are positive argon ions and electrons. Diluted whole blood samples are converted into an aerosol using a nebulizer inserted within a spray chamber. A portion of the aerosol is transported through the spray chamber and then through the central channel of the plasma, where it experiences temperatures of 6000–8000 ^oK. This thermal energy atomizes and ionizes the sample. The ions, along with the argon, enter the mass spectrometer through an interface that separates the ICP, operating at atmospheric pressure (approximately 760 torr), from the mass spectrometer, operating at approximately 10-5 torr. The mass spectrometer permits detection of ions at each mass-to-charge ratio in rapid sequence, allowing individual isotopes of an element to be determined. Once inside of the mass spectrometer, the ions pass through the ion optics, then the mass analyzing quadrupole before being detected as they strike the surface of the detector. The ion optics focuses the ion beam using an electrical field.

Electrical signals resulting from the detection of the ions are processed into digital information that is used to indicate the intensity of the ions and subsequently the concentration of the element. In this method blood samples are diluted with 18 M-ohm water and with diluent, containing 1% v/v tetramethylammonium hydroxide (TMAH), 0.05% disodium ethylenediamine tetraacetate (EDTA), 5% ethyl alcohol, 0.05% Triton X-100?, Au is added to reduce intrinsic Hg memory effects, Rh for internal standardization of Cd, and Bi for internal standardization of Hg and Pb [11-13]. The samples were prepared with the following ratio Sample: Water: Diluent = 1:1:48 correspondingly.

There were no changes (from the previous 2 years of NHANES) to equipment, lab methods or lab site. Testing for selenium and manganese was added in 2011.

Data Processing and Editing

Five additional variables were created for this data file. The formula for their creation is as follows: 

• The cadmium in µg/L was converted to nmol/L by multiplying by 8.897. 
• The lead in µg/dL was converted to µmol/L by multiplying by 0.0483.
• The manganese in µg/L was converted to nmol/L by multiplying by 18.202.
• The selenium in µg/L was converted to µmol/L by multiplying by 0.0127.
• The mercury in µg/L was converted to nmol/L by multiplying by 4.99.

Detection Limits
The detection limit for all analytes was constant in the data set. The lower detection limits for lead were 0.25 µg/dL and 0.16 µg/L for cadmium, selenium was 30 ug/L, manganese was 1.06 ug/L, and 0.16 µg/L for total mercury.

Laboratory Quality Assurance and Monitoring

The NHANES quality assurance and quality control (QA/QC) protocols meet the 1988 Clinical Laboratory Improvement Act mandates. Read the General Documentation of Laboratory Data file for detailed QA/QC protocols. Detailed QA/QC instructions are discussed in the NHANES Laboratory/Medical Technologists Procedures Manual (LPM).

Analytic Notes

Refer to the 2011-2012 Laboratory Data Overview for general information on NHANES laboratory data.

The analysis of NHANES 2011-2012 laboratory data must be conducted using the appropriate survey design and demographic variables. The NHANES 2011-2012 Demographics File contains demographic data, health indicators, and other related information collected during household interviews as well as the sample weight variables. The Fasting Questionnaire File includes auxiliary information such as fasting status, the time of venipuncture, and the conditions precluding venipuncture. The demographics and fasting questionnaire files may be linked to the laboratory data file using the unique survey participant identifier (i.e., SEQN).

In cases, where the result was below the limit of detection, the value for that variable is the detection limit divided by the square root of two.

Exam sample weights should be used for analyses. Please refer to the NHANES Analytic Guidelines and the on-line NHANES Tutorial  for further details on the use of sample weights and other analytic issues.

Codebook and Frequencies